In the manufacture of semiconductor devices, it is desirable to provide relatively small diameter openings to contact areas of the device. One limitation in doing this is the diameter of openings utilized in photomasks to expose areas of photoresist covering the materials to be etched. It is desirable to produce openings which are smaller than those otherwise available using the photomask along with a light exposing the photoresist. This has been achieved in a prior art by after exposing the photoresist with a photomask, etching a via down to the surface to be contacted. Next a liner material is applied to the via and the surface to be contacted. After deposition of the liner material, an anisotropic etch is performed. Because of the nature of anisotropic etching, the liner material at the bottom of the aperture is etched and removed, while a portion of the liner material is retained during this etch process. The surface to be contacted at the bottom of the via is thus etched once again, damaging the substrate material which will ultimately be contacted by an electrical connection.
Thus it will be appreciated that in the prior art technique, the first etch opens the via down to the surface to be contacted and this is followed by the application of the liner of material and subjecting the liner material to anisotropic etching. Using this prior art process results in a double etch of the material at the base of the opening, thus unnecessarily damaging that material in advance of providing a contact to the material at the base of the via.
Thus what is needed is a process by which only a single etch is utilized to open the contact area at the base of the via while concurrently establish a liner covering the interior walls of the via.